brakes problem need help

My brakes was losing pressure.. so i service the master cylinder with a service kit .. i reinstall the master cylinder and bleed the entire system and it worked perfect . Now when i drive my car for a short distance , the brakes seize up completely.( during the drive i have used the brakes like 3 times). I then service the 2 front brakes .. and the same problem occured .. Is there anything wrong with my booster or is it my master cylinder... i Have an toyota AT 170 carina... any advice will be helpful.. thanx im completely in darkness here

Does the brake pedal return to normal height when you let off it? If not, then the master cylinder piston is sticking. I don't know what all is included in the "service kit", but a pressure loss should be cause for replacing the whole MS versus just the internal seals. Any internal scoring damage done to the cylinder body can't be fixed with a new seal. And improperly installed o-rings/seals or even oversized seals can end up binding within the cylinder. I'm sure you tried to keep the cost down and probably checked the cylinder bore, but sometimes its just better to buy the whole thing.

If it does return to normal height then the brakes themselves are sticking and/or there's a problem with the ABS (if equipped). It could be a plugged brake line, sticking brake cylinder, or sticking caliper slide pins. But usually these problems don't happen on both sides simultaneously...you'll feel pulling to one side or the other.

Hope this helps!